Lettuce is the common name for leaf lettuce, which belongs to the genus Lettuce in the family Asteraceae. For annual or biennial herbaceous crops, it is a very common edible vegetables. It is a very common edible vegetable. It is also a popular vegetable in Europe and the United States, and is well loved by people. Lettuce is native to the Mediterranean coast of Europe, domesticated from wild species. Ancient Greeks and Romans were the first to eat. Lettuce imported into our country has a long history, the southeastern coast, especially in the suburbs of large cities, the two regions cultivated more, especially in Taiwan planting is particularly common. In recent years, the cultivation area is rapidly expanding, lettuce from hotels, restaurants into the ordinary people's tables. People in China, Japan and other countries tend to cook it and eat it, and in Western culture people tend to put it in salads, hamburgers and other foods to eat it raw.
Lettuce according to the color of the leaves to distinguish between green lettuce, purple lettuce two. If you distinguish by the state of growth of the leaves, there are loose leaf lettuce, ball lettuce
two kinds of lettuce. The latter leaves are clasped together in a ball shape. If further subdivided there are three types of ball lettuce, one is the leaf blade is obovate, leaf and smooth, soft texture, leaf edge slightly corrugated cream lettuce; there is another leaf blade is inverted ovoid, leaf surface crumpled, brittle texture, leaf edge is serrated crisp leaf lettuce. The latter is more commonly cultivated; bitter-leaf lettuce has thick, long oval leaves, leaves that are entire and half-knotty. The single plant of loose leaf lettuce weighs 250-500 grams, and the nodular lettuce has a longer growing period than loose leaf lettuce, and the single plant weighs a lot more, generally in the range of 400-750 grams, and the late-maturing varieties with a long growing period can reach more than 1,000 grams. Lettuce root system is shallow, fibrous roots developed, the main root group distribution in the surface 20 cm soil layer, stem shortening, leaf alternate, lanceolate, elliptic, oval, etc., leaf color green, yellow-green or purple, leaf surface spreading or crumpled, leaf margin undulate or lobed, outer leaves to develop, the heart of the leaves loose or hold into the ball of the leaves, seeds gray or black-brown, a thousand grains of weight of about 1 gram.
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Introduction of lettuce
Lettuce nodules like cool climate, the growth of the appropriate temperature of 15-20 ℃, the most suitable for the day and night temperature difference, the night temperature is lower environment. Knotting temperature of 10-16 ℃, the temperature exceeds 25 ℃, the ball of the leaf inside the high temperature will cause necrosis and decay of the heart leaf, and poor growth. Seed germination temperature of 15-20 ℃, higher than 25 ℃, because the seed coat water absorption is blocked, poor germination. Lettuce in the summer sowing needs low-temperature treatment, soak the seeds in the refrigerator after the freezer to germinate, to be buds white before sowing, before sowing, the application of the new high-fat film mixing seeds. The loose-leaf lettuce is more heat-resistant, but in the hot season, it also grows poorly. Lettuce like slightly acidic soil (pH 6-6.3 is the best), with strong water retention, well-drained sandy loam or clay loam cultivation is preferred. Lettuce needs more nitrogen fertilizer, so the base fertilizer before planting should be more organic fertilizer, the growth process, no more organic fertilizer. During the growth period can not lack of water, especially the balling lettuce balling period, need sufficient water, such as dry early lack of water, not only the leaf ball small, and leaf taste bitter, poor quality. But the water can not be too much, otherwise the leaf ball will be scattered, affecting the appearance of quality, but also easy to lead to the occurrence of soft rot and botrytis. Only appropriate water and fertilizer management, and in the growth stage of the timely spraying of strong stem spirit, in order to obtain high-yield and high-quality lettuce.
Lettuce is a half-hardy vegetables, like cool and moist climatic conditions, intolerance of heat. In areas with hot summers, attention should be paid to the seedling period when cultivating in the fall to take cooling measures and pay attention to the problem of moss extraction in the first period. If you want an annual supply, you should use a combination of open field and protected area production, basically to meet the demand throughout the year.
Lettuce is rich in vitamins and minerals, and it is easy to obtain pollution-free products without using pesticides in the cultivation process.
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Introduction of Lettuce
When we make cold dishes, many people think of lettuce. From the name we can easily see that lettuce is the best vegetable to eat raw. Lettuce is rich in nutrients and has more fiber and vitamin C than cabbage. In addition to raw and stir-fried, lettuce can also be stir-fried with garlic, oyster sauce, tofu, mushrooms, and different combinations, lettuce plays a different role.
Stir-fried lettuce: lettuce itself has the effect, such as analgesic hypnotic, lower cholesterol, assist in the treatment of neurasthenia, diuretic, promote blood circulation, antiviral and so on.
Garlic lettuce: In addition to the effects of stir-fry lettuce, there are sterilization, anti-inflammatory and hypoglycemic effect, and can even supplement the brain. Lettuce is rich in vitamins, with the prevention of bleeding gums and vitamin C deficiency and other effects. Garlic has the effect of detoxification, stagnation, stomach, cold pain in the stomach and abdomen, dysentery, diarrhea, consumption, whooping cough, colds, malaria and other diseases have a certain therapeutic effect.
Oyster sauce lettuce: oyster sauce is not oily, but in the processing of oyster sauce (also known as oyster sauce), cooking oyster sauce the rest of the soup, this soup is filtered and concentrated oyster sauce. Oyster sauce is a flavorful seasoning that contains a variety of nutrients. Therefore, oyster sauce lettuce in addition to lowering blood lipids, lowering blood pressure, lowering blood sugar, promote intellectual development and anti-aging effects, but also diuretic, promote blood circulation, anti-virus, prevention and treatment of heart disease and liver disease.
Lettuce and nutritious tofu with food, is a high-protein, low-fat, low-cholesterol, multi-vitamin dishes, has a clear liver and gallbladder, nourishing Yin and tonifying the kidney, whitening the skin, weight loss and bodybuilding effect. The eye red swelling pain, lung heat cough, thirst, spleen deficiency and abdominal distension also has a certain therapeutic effect; and mushrooms are rich in easily absorbed proteins, and has the spleen and qi, moistening phlegm as well as a strong nourishing effect, and lettuce with food, on the heat of the cough, phlegm, chest tightness, vomiting and diarrhea, etc. has a certain therapeutic effect.
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Introduction of lettuce
When you are selecting lettuce, the most important thing is of course to first observe whether the color of the leaves is green. Furthermore, it is to pay attention to the stem of the lettuce. Generally speaking, lettuce is fresh if the stem color is whitish.
Perhaps you've heard that good lettuce has a name, "glass lettuce," in some places. As the name suggests, good lettuce doesn't look as clear as real glass, but it is a good indicator of the texture of good lettuce. Generally speaking, the better the lettuce, the crunchier its leaves are, which can be felt by pinching the leaves with your hand. Also, the leaves are not very thick, and the leaf surface has an attractive glossy sheen; if you put a drop of water on the front side of the leaf, the drop will not bloom. Where there are breaks or folds in the leaf surface, unfresh lettuce will become as if it had rust spots due to air oxidation, while fresh lettuce will not be so.